Mountain Ranges

 import java.util.*;

public class MountainRanges {

    public static int mountainRanges(int n) {

        int dp[] = new int[n + 1];

        dp[0] = 1;

        dp[1] = 1;

        for (int i = 2; i <= n; i++) {

            for (int j = 0; j <= i - 1; j++) {

                int upstroke = dp[j];

                int downstroke = dp[i - j - 1];

                dp[i] += upstroke * downstroke;

            }

        }

        return dp[n];

    }

    public static void main(String[] args) {

        System.out.println("Enter no.of pairs:");

        Scanner sc = new Scanner(System.in);

        int pairs = sc.nextInt();

        System.out.println("No.of mountain ranges: " + mountainRanges(pairs));

    }

}